This invention relates to a semiconductor device and a production method thereof. More particularly, the present invention relates to a technique of improving the breakdown voltage of a semiconductor device which incorporates a bipolar IC and a CMOS (Complementary Metal Oxide Semiconductor Field Effect Transistor) IC in one semiconductor chip (hereinafter referred to as "BiCMOS IC").
The operation speed and packaging density of bipolar ICs tend to increase more and more, and progress has been made in miniaturization techniques and self-alignment techniques, using selective oxide films as means for accomplishing these objects. On the other hand, in using such selective oxide films for accomplishing such objects, problems have occurred in that the production process becomes more complicated and the breakdown voltage drops. These problems are discussed in "Nikkei Electronics", 1983, June 20, pp. 179-207, published by Nikkei-McGrawHill Co.